This invention relates to liquid chromatographic methods and apparatuses.
Inexpensive liquid chromatographic apparatuses have been developed and are in use, particularly for preparatory chromatography where the emphasis is on quickly obtaining relatively large numbers of large samples at low cost. Such systems generally include at least one solvent reservoir, a multiple pump, a controller, multiple chromatographic columns, a collector and usually a multiple detector. Commonly, provision is made for a gradient to be developed and such gradient systems require at least two solvent reservoirs and some mechanism for mixing the solvent from each of the two reservoirs together to form a gradient for application to the column. Because of the cost of individual detectors, one for each column, the detector may be multiplexed.
The prior art apparatuses have a disadvantage in that they are not as inexpensive as desired, require a longer period of time than desired for the separation or have reduced sensitivity due to multiplexing noise.